Identification of Chalcogen Defects in Silicon

We show how self-consistent total-energy calculations can be used to identify the position of defects in semiconductors. Despite intensive experimental research on S, Se and Te point defects in Si, it has remained unclear whether these impurities occupy substitutional or Td-interstitial sites. Our Green-function total-energy calculations show that the substitutional site is favored by several eV and therefore the stable defect position is identified as substitutional. We further consider the formation energies of distant defect pairs consisting of a substitutional chalcogen and a Si self-interstitial and we study the reaction where the two constituents change places.